I would like to know the best way to calculate space, every time that I am creating a PO dataset. Example: If I want to create a dataset with 40 members. What would be the best way to calculate the space.

The size of PO dataset will depend on the size of members, not the number of them. and you will have to know the total size of all members to allocate the PO with exactly the same size. If the members are constant, then you can write some utility to findout the space.

Hi friend,
first you have to think that,
how much amount of data you have to fetch (or) code in to the dataset,
for example you have to fetch 500 bytes of data according to that we have to allocate the size of the dataset.